Unusual Designated-Tailoring on Zone-Axis Preferential Growth of Surfactant-Free ZnO Mesocrystals

An unusual designated-tailoring on zone-axis preferential growth of surfactant-free ZnO mesocrystals with different features (shapes and sizes) was successfully achieved via an additive-free complex-precursor solution method. The formation of ZnO mesocrystals here is essentially determined by the characteristic of [Zn(OH)4]2– precursors, and an oriented nanoparicle aggregation with tailoring sizes and shapes can occur in different concentration of reactants at higher reaction temperature. Spindle-like ZnO mesocrystals with tunable sizes (along the c-axis direction) were synthesized by adjusting the concentration of hydroxyl ions, and peanut-like ZnO mesocrystals with controllable sizes (along the c-axis direction) and shapes (perpendicular c-axis direction) were prepared by tailoring the concentration of zinc ions. Structural and morphological evolutions were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and field-emission scanning electron microscopy (FESEM). The study is of great significance in bottom-up assembly of controllable ordering architectures, and provides a good opportunity to understand the formation mechanism and fundamental significance of zone-axis preferential growth of ZnO mesocrystals. Significantly, it is believed that the precursor driven assembly of mesostructures reported here would provide a green way to design more and more surfactant-free metal oxide architectures with well-defined shapes.